Frequently we need to make some of the fields in layout of a view are mandatory.To do this every element has a property state(Normal item and Required ) to make the field is optional or mandatory.Although we select the option Required of state of field property to make the element mandatory.It will not trigger the error message even the field is not filled with any value when you are continuing with the 'Submit' button of the form .
To trigger the error message when the user is leaving the blank value in the mandatory field and continuing with the form.Write the logic given below in the 'OnAction' event of event handler method to raise the error message that 'Fill in all required entry fields' .
method ONACTIONCLICK .
* Data declaration
lo_view_controller type ref to if_wd_view_controller,
lo_dyn type ref to cl_wd_dynamic_tool.
* Create Object
create object lo_dyn.
data lt_messages type lo_dyn->t_check_result_message_tab.
* Get view controller reference
lo_view_controller = wd_this->wd_get_api( ).
* Call Method to verify the element has the value or not
call method cl_wd_dynamic_tool=>check_mandatory_attr_on_view
view_controller = lo_view_controller
display_messages = ABAP_TRUE
messages = lt_messages .